Most of known antitumor agents are of low molecular weights and rely on their direct cytotoxic effect on tumor cells in vivo, so that they have a high toxicity against host animals, giving unfavorable effect thereon. On the other hand, some polysaccharides having a relatively high molecular weight, a low toxicity and significant immunopotenciating and antitumor properties have been used in the form of a partially purified powder derived from diverse sources including higher plants, fungi, lichen, bacteria and yeasts by extraction, but they are narrow in antitumor spectra and thus have limited applications in practical purposes.
It has already been reported that some antitumor materials are obtained from shellfish (see Japanese Patent Publication No. 8088/82 and Japanese Patent KOKAI Nos. 41314/79 and 41315/79). According to these publications, the antitumor materials are prepared by a process comprising (1) removing shells from raw shellfish with or without heating the latter, (2) removing the liver from the meat, (3) finely cutting or grinding the resulting meat in an aqueous solvent such as water and a saline solution at a low temperature by means of a blender and the like, optionally followed by sonication or other physical impact treatment whereby to attain high homogenization of the finely divided meat pieces with good extraction of desired antitumor materials in the cold aqueous solvent, (4) removing all the water-insoluble materials including the exhausted meat pieces from the resulting mixture by centrifuging or other means and (5) isolating the desired antitumor materials from the extract thus obtained by purification means known for the isolation of protein substances such as dialysis, ultrafiltration, gel-filtration and column chromatography. The antitumor materials thus obtained from shellfish are interested in that they have broad antitumor spectra and high therapeutic activities. However, the processes hitherto proposed for the preparation of these materials as above-mentioned have such disadvantages that they have to spend the edible portions of shellfish being expensive, require complicated procedures for the extraction of desired materials and involve problems on disposal of the spent residue of meat pieces in large amount, so that it seems difficult to provide these materials on an industrial scale through these processes.
We have made our investigations with the intention of providing a process acceptable for the purpose of industrial production of antitumor materials of a kind similar to those derived from the meat of shellfish as above-mentioned and have now found that the liquid portion which comes from cooking of raw shellfish carried out in a hot aqueous solvent or with vapor of such solvent to take up edible portion thereof and which is to be discarded as waste can serve as raw material from which water-soluble, macromolecular glycoprotein substances useful as antitumor agent is recovered and that these substances have a range of molecular weights within the limits of from 10,000 to 300,000 and can be recovered efficiently by certain combination of purification techniques. The liquid portion coming from cooking of raw shellfish has hiterto been discarded as waste with costly additional treatment required to avoid environmental contamination and is hereinafter referred to as "waste liquor".